(function($) {
	function drag(e) {
		var state = $.data(e.data.target, 'draggable');
		var opts = state.options;
		var proxy = state.proxy;

		var dragData = e.data;
		var left = dragData.startLeft + e.pageX - dragData.startX;
		var top = dragData.startTop + e.pageY - dragData.startY;

		if (proxy) {
			if (proxy.parent()[0] == document.body) {
				if (opts.deltaX != null && opts.deltaX != undefined) {
					left = e.pageX + opts.deltaX;
				} else {
					left = e.pageX - e.data.offsetWidth;
				}
				if (opts.deltaY != null && opts.deltaY != undefined) {
					top = e.pageY + opts.deltaY;
				} else {
					top = e.pageY - e.data.offsetHeight;
				}
			} else {
				if (opts.deltaX != null && opts.deltaX != undefined) {
					left += e.data.offsetWidth + opts.deltaX;
				}
				if (opts.deltaY != null && opts.deltaY != undefined) {
					top += e.data.offsetHeight + opts.deltaY;
				}
			}
		}

		if (e.data.parent != document.body) {
			left += $(e.data.parent).scrollLeft();
			top += $(e.data.parent).scrollTop();
		}

		if (opts.axis == 'h') {
			dragData.left = left;
		} else if (opts.axis == 'v') {
			dragData.top = top;
		} else {
			dragData.left = left;
			dragData.top = top;
		}
	}

	function applyDrag(e) {
		var state = $.data(e.data.target, 'draggable');
		var opts = state.options;
		var proxy = state.proxy;
		if (!proxy) {
			proxy = $(e.data.target);
		}
		proxy.css({
			left : e.data.left,
			top : e.data.top
		});
		$('body').css('cursor', opts.cursor);
	}

	function doDown(e) {
		if (!$.fn.draggable.isDragging) {
			return false;
		}

		var state = $.data(e.data.target, 'draggable');
		var opts = state.options;

		var droppables = $('.droppable').filter(function() {
			return e.data.target != this;
		}).filter(function() {
			var accept = $.data(this, 'droppable').options.accept;
			if (accept) {
				return $(accept).filter(function() {
					return this == e.data.target;
				}).length > 0;
			} else {
				return true;
			}
		});
		state.droppables = droppables;

		var proxy = state.proxy;
		if (!proxy) {
			if (opts.proxy) {
				if (opts.proxy == 'clone') {
					proxy = $(e.data.target).clone().insertAfter(e.data.target);
				} else {
					proxy = opts.proxy.call(e.data.target, e.data.target);
				}
				state.proxy = proxy;
			} else {
				proxy = $(e.data.target);
			}
		}

		proxy.css('position', 'absolute');
		drag(e);
		applyDrag(e);

		opts.onStartDrag.call(e.data.target, e);
		return false;
	}

	function doMove(e) {
		if (!$.fn.draggable.isDragging) {
			return false;
		}

		var state = $.data(e.data.target, 'draggable');
		drag(e);
		if (state.options.onDrag.call(e.data.target, e) != false) {
			applyDrag(e);
		}

		var source = e.data.target;
		state.droppables.each(function() {
			var dropObj = $(this);
			if (dropObj.droppable('options').disabled) {
				return;
			}

			var p2 = dropObj.offset();
			if (e.pageX > p2.left && e.pageX < p2.left + dropObj.outerWidth() && e.pageY > p2.top && e.pageY < p2.top + dropObj.outerHeight()) {
				if (!this.entered) {
					$(this).trigger('_dragenter', [ source ]);
					this.entered = true;
				}
				$(this).trigger('_dragover', [ source ]);
			} else {
				if (this.entered) {
					$(this).trigger('_dragleave', [ source ]);
					this.entered = false;
				}
			}
		});

		return false;
	}

	function doUp(e) {
		if (!$.fn.draggable.isDragging) {
			clearDragging();
			return false;
		}

		doMove(e);

		var state = $.data(e.data.target, 'draggable');
		var proxy = state.proxy;
		var opts = state.options;
		if (opts.revert) {
			if (checkDrop() == true) {
				$(e.data.target).css({
					position : e.data.startPosition,
					left : e.data.startLeft,
					top : e.data.startTop
				});
			} else {
				if (proxy) {
					var left, top;
					if (proxy.parent()[0] == document.body) {
						left = e.data.startX - e.data.offsetWidth;
						top = e.data.startY - e.data.offsetHeight;
					} else {
						left = e.data.startLeft;
						top = e.data.startTop;
					}
					proxy.animate({
						left : left,
						top : top
					}, function() {
						removeProxy();
					});
				} else {
					$(e.data.target).animate({
						left : e.data.startLeft,
						top : e.data.startTop
					}, function() {
						$(e.data.target).css('position', e.data.startPosition);
					});
				}
			}
		} else {
			$(e.data.target).css({
				position : 'absolute',
				left : e.data.left,
				top : e.data.top
			});
			checkDrop();
		}

		opts.onStopDrag.call(e.data.target, e);

		clearDragging();

		function removeProxy() {
			if (proxy) {
				proxy.remove();
			}
			state.proxy = null;
		}

		function checkDrop() {
			var dropped = false;
			state.droppables.each(function() {
				var dropObj = $(this);
				if (dropObj.droppable('options').disabled) {
					return;
				}

				var p2 = dropObj.offset();
				if (e.pageX > p2.left && e.pageX < p2.left + dropObj.outerWidth() && e.pageY > p2.top && e.pageY < p2.top + dropObj.outerHeight()) {
					if (opts.revert) {
						$(e.data.target).css({
							position : e.data.startPosition,
							left : e.data.startLeft,
							top : e.data.startTop
						});
					}
					$(this).trigger('_drop', [ e.data.target ]);
					removeProxy();
					dropped = true;
					this.entered = false;
					return false;
				}
			});
			if (!dropped && !opts.revert) {
				removeProxy();
			}
			return dropped;
		}

		return false;
	}

	function clearDragging() {
		if ($.fn.draggable.timer) {
			clearTimeout($.fn.draggable.timer);
			$.fn.draggable.timer = undefined;
		}
		$(document).unbind('.draggable');
		$.fn.draggable.isDragging = false;
		setTimeout(function() {
			$('body').css('cursor', '');
		}, 100);
	}

	$.fn.draggable = function(options, param) {
		if (typeof options == 'string') {
			return $.fn.draggable.methods[options](this, param);
		}

		return this.each(function() {
			var opts;
			var state = $.data(this, 'draggable');
			if (state) {
				state.handle.unbind('.draggable');
				opts = $.extend(state.options, options);
			} else {
				opts = $.extend({}, $.fn.draggable.defaults, $.fn.draggable.parseOptions(this), options || {});
			}
			var handle = opts.handle ? (typeof opts.handle == 'string' ? $(opts.handle, this) : opts.handle) : $(this);

			$.data(this, 'draggable', {
				options : opts,
				handle : handle
			});

			if (opts.disabled) {
				$(this).css('cursor', '');
				return;
			}

			handle.unbind('.draggable').bind('mousemove.draggable', {
				target : this
			}, function(e) {
				if ($.fn.draggable.isDragging) {
					return
				}
				var opts = $.data(e.data.target, 'draggable').options;
				if (checkArea(e)) {
					$(this).css('cursor', opts.cursor);
				} else {
					$(this).css('cursor', '');
				}
			}).bind('mouseleave.draggable', {
				target : this
			}, function(e) {
				$(this).css('cursor', '');
			}).bind('mousedown.draggable', {
				target : this
			}, function(e) {
				if (checkArea(e) == false)
					return;
				$(this).css('cursor', '');

				var position = $(e.data.target).position();
				var offset = $(e.data.target).offset();
				var data = {
					startPosition : $(e.data.target).css('position'),
					startLeft : position.left,
					startTop : position.top,
					left : position.left,
					top : position.top,
					startX : e.pageX,
					startY : e.pageY,
					offsetWidth : (e.pageX - offset.left),
					offsetHeight : (e.pageY - offset.top),
					target : e.data.target,
					parent : $(e.data.target).parent()[0]
				};

				$.extend(e.data, data);
				var opts = $.data(e.data.target, 'draggable').options;
				if (opts.onBeforeDrag.call(e.data.target, e) == false)
					return;

				$(document).bind('mousedown.draggable', e.data, doDown);
				$(document).bind('mousemove.draggable', e.data, doMove);
				$(document).bind('mouseup.draggable', e.data, doUp);

				$.fn.draggable.timer = setTimeout(function() {
					$.fn.draggable.isDragging = true;
					doDown(e);
				}, opts.delay);
				return false;
			});

			// check if the handle can be dragged
			function checkArea(e) {
				var state = $.data(e.data.target, 'draggable');
				var handle = state.handle;
				var offset = $(handle).offset();
				var width = $(handle).outerWidth();
				var height = $(handle).outerHeight();
				var t = e.pageY - offset.top;
				var r = offset.left + width - e.pageX;
				var b = offset.top + height - e.pageY;
				var l = e.pageX - offset.left;

				return Math.min(t, r, b, l) > state.options.edge;
			}

		});
	};

	$.fn.draggable.methods = {
		options : function(jq) {
			return $.data(jq[0], 'draggable').options;
		},
		proxy : function(jq) {
			return $.data(jq[0], 'draggable').proxy;
		},
		enable : function(jq) {
			return jq.each(function() {
				$(this).draggable({
					disabled : false
				});
			});
		},
		disable : function(jq) {
			return jq.each(function() {
				$(this).draggable({
					disabled : true
				});
			});
		}
	};

	$.fn.draggable.parseOptions = function(target) {
		var t = $(target);
		return $.extend({}, $.parser.parseOptions(target, [ 'cursor', 'handle', 'axis', {
			'revert' : 'boolean',
			'deltaX' : 'number',
			'deltaY' : 'number',
			'edge' : 'number',
			'delay' : 'number'
		} ]), {
			disabled : (t.attr('disabled') ? true : undefined)
		});
	};

	$.fn.draggable.defaults = {
		proxy : null, // 'clone' or a function that will create the proxy object,
		// the function has the source parameter that indicate the source object dragged.
		revert : false,
		cursor : 'move',
		deltaX : null,
		deltaY : null,
		handle : null,
		disabled : false,
		edge : 0,
		axis : null, // v or h
		delay : 100,

		onBeforeDrag : function(e) {
		},
		onStartDrag : function(e) {
		},
		onDrag : function(e) {
		},
		onStopDrag : function(e) {
		}
	};

	$.fn.draggable.isDragging = false;

})(jQuery);
